Passive delay timer



United States Patent [72] Inventor David W. Rabenhorst,

Silver Spring, Maryland [21 Appl. No. 707,592 [22] Filed Feb. 23, 1968[45] Patented Sept. 15, 1970 [73] Assignee By mesne assignments, to theUnited States of America as represented by the Secretary of the Navy[54] PASSIVE DELAY TIMER 4 Claims, 3 Drawing Figs. [52] US. Cl 92/35,92/38, 92/84, 92/143, 73/407, 73/410 [51] Int. Cl. .4 F16j 3/00, FOlb19/04 [50] Field of Search 92/8, 35, 37, 38, 84, 97, 143; 137/78,8l;73/410, 407; 251/54 [56] References Cited UNITED STATES PATENTS2,312,201 2/1943 Thompson et al. 92/35X 2,389,412 11/1945 Carlton 92/35X2,403,186 2/"1946 Leslie 137/81X 2,453,841 11/1948 Gluzek 92/35X2,466,071 4/1949 Barnes et al. 73/410X 2,469,038 5/1949 Winkler 251/54XKain 2,580,433 l/1952 251/54X 2,635,581 4/1953 Karig.... 92/35X2,773,482 12/1956 Dickie 92/35X 2,795,239 6/1957 Eckman et al. 92/372,815,705 12/1957 Jensen l37/81X 2,816,561 12/1957 Krueger 137/812,963,034 12/1960 Cummins 137/81 2,988,282 6/1961 Hotten Roth 92/35X3,400,638 9/1968 McEvoy 92/38X Primary Examiner-Martin P. SchwadronAssistant Examiner-Leslie J. Payne Altorneys.lustin P. Dunlavey and JohnO. Tresansky ABSTRACT: A passive delayed timing device, comprisingfluid-containing chambers at standard atmospheric pressure,

which, on exposure to a lower pressure environment such as PatentedSept. 15, 1970 DAVID W. RABENHORST INVENTOR ATTORNEY PASSIVE DELAY TIMERBACKGROUND OF THE INVENTION 1. Field of the Invention Timing deviceshave long been used aboard spacecraft to perform such necessaryfunctions as initiation of antenna erection, boom deployment, highvoltage equipment turn-on, cover removal, and stage separation. Timersnow employed are generally electrical or mechanical with certainspecific timers utilizing the sublimation properties of substances suchas biphenyl. In operation, the subject invention must be considered apassive pneumatic device, its sole input being exposure to an externalpressure lower than that pressure initially present within the device.

2. Description of the Prior Art Advantages of the present inventionrelative to prior devices used for a like purpose will be hereinafterdescribed more completely, along with comments pertinent thereto in thesummary of the invention.

The present invention utilizes pressure differentials to actuate a fluidmetering delay device. Grant and Hubby in respective U.S. Pat. No.2,663,153 of December 22, I953, and U.S. Pat. No. 3,152,611 of October23, 1964, disclose delay timers which use gas pressure to force fluidthrough a slow metering orifice. However, the delay timers of Grant andHubby each require a large source of pressurized gas, whereas thesubject invention requires only a small capsule of air packaged underordinary atmospheric conditions. Additionally, the present invention isautomatically triggered when exposed to a low-pressure environment,whereas the prior art devices require manual setting. More importantly,the above-mentioned devices of the prior art do not demonstrate theextremely long timing cycles within the capability of the subjectinvention nor can said devices be of practical use on a spacecraft dueto weight considerations.

SUMMARY OF THE INVENTION Work functions aboard a spacecraft mustoften beinitiated after launch. Timing cycles aboard the spacecraft orgroundinitiated radio signals provide the two major methods foraccomplishing actuation of such functions. Self-contained timers possesscertain advantages over radio signals in that timers require simplerinstrumentation and therefore are less costly, proximity to radio signaltransmitting stations is rendered unnecessary, and timers generallyweigh less than radio receivers and supporting equipment, therebyconserving weight for payload applications.

Timers now in use range from the traditional electrical and mechanicalmechanisms to devices basing their timing cycles on physical or chemicalproperties of various compounds, such as sublimation switches usingbiphenyl. The passive timer disclosed herein comprises a pneumaticdevice whbse sole input is exposure to the vacuum of outer space.Expandible capsules of fluids at differing pressures cause movement ofan output shaft, thus providing force for the accomplishment of a workcycle or for the initiation of work cycles through a triggering systemwhich then produces the desired output. In the various embodiments ofthe present invention, an accurate fluid metering system sensitive tothese slight pressure differentials caused by exposure to a low pressureenvironment is essential.

It is therefore an object of the invention to provide a selfcontainedtiming device possessing a substantial shelf life even in a launch-readyconfiguration despite temperature changes, normal handlingcontamination, humidity changes, and assembly and testing procedures.

It is another object of the invention to provide a passive timing deviceimmune to RF, static, or other electrical background disturbances, andwhich requires no batteries, Wiring or electrical instrumentation foroperation.

It is still another object of the invention to provide a relativelylightweight and compact delayed timing device which has no functional orphysical interface with a launch vehicle and which can be integratedinto existing spacecraft systems.

It is a further object of the invention to provide an accurate delayedtiming device with timing cycles of from a few minutes up to one year,and which may be tested any number of times before launch without itsdestruction or impairment to its subsequent use.

Further objects and advantages of the invention will become more readilyapparent from the following detailed description of the preferredembodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-section of a firstembodiment of the invention;

FIG. 2 is a cross-section of a second embodiment of the invention,showing the concentric expandible chamber; and

FIG. 3 is a cross-section of a third embodiment of the inventron.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings andfirst to FIG. 1 thereof, one embodiment of the invention is showngenerally at l and includes a cylindrical casing 2 which defines a firstfluid storage chamber 3. The outer end of the casing is closed by a wallplate 4. At its inner end the casing 2 isprovided with a wall plate 5which is formed with an axial extension 6 that is closed at its free endby a wall plate 7 having a port 8 therein. The extension 6 issubstantially one-half the diameter of the casing 2 and defines a secondstorage chamber 9 which is vented to ambient pressure through the port8.

Mounted for sliding movement in the extension 6 is an expandible chamber10, a bellows in the embodiment shown, which is closed at its inner endby a plate 11 that also serves to close the inner end of the chamber 9.The outer end of the chamber 10 is closed by a plate 12, and secured tothe plate 12 is a plunger 13 having an actuator rod 14 that slidablyextends through the wall plate 7 axially thereof.

A second expandible chamber 15 of bellows configuration is secured tothe inner surface of the wall plate 4 within the chamber 3 and is closedat its opposite ends, thereby defining a pressure tight chamber. Thechamber 15 is expandible within the chamber 3 and contains a gas, suchas air, which is at atmospheric pressure when the bellows of the chamber15 is in a contracted position.

Positioned within the chamber 3 and connected to the plate 1 1 is ametering valve 16 which communicates between the interior of saidchamber and the interior of the expandible chamber 10. The valve 16,which may conveniently be the well-known Viscojet, manufactured by theLee Company of Westbrook, Connecticut slowly meters a fluid, such aspropyl alcohol or a gas such as air, from the chamber 3 into theexpandible chamber 10. The fluid used depends principally on the rate ofmetering desired, since a liquid would pass through the valve 16 at aslower rate than would a gas.

When the passive timer thus described is subjected to an ambientpressure equal to standard atmospheric pressure, pressures in all of theaforementioned chambers are equal and the system is completely passive.If the passive timer is placed in a vacuum, or in an ambient pressureenvironment wherein the pressure is less than standard atmosphericpressure, such as the vacuum of outer space, gas within the secondstorage chamber 9 will escape through port 8 and create a low pressureregion acting on plate 12 of expandible chamber 10. Expandible chamber15 containing a gas at a pressure of one atmosphere feels" this pressuredifferential across expandible chamber 10 and expands slowly,communicating force to the fluid contained in fluid storage chamber 3,and thereby' causing said fluid to be contained at a higher pressurethan that fluid in expandible chamber 10. Said fluid is thus meteredthrough the metering valve 16 into expandible chamber 10, creating aforce tending to expand said chamber 10. The expandible chamber 10, onovercoming friction, thereby expands and advances plunger 13 toward wallplate 7 which causes the actuator rod 14 to move outwardly of said wallplate 7 and thereby to actuate a trigger mechanism (not shown) whichaccomplishes boom deployment, equipment turn-on, stage separation, orany other desired effect. The timing cycle as represented by the slow,steady progression of the acutator rod is divorced from the output cycleas represented by the trigger mechanism, since the force of the actuatorrod is not employed to perform the work cycle, only to actuate it. Sincetiming accuracy depends on having a known and reasonably steady load onthe actuator rod during the timing cycle, varying forces required todirectly produce different work functions could conceivably cause errorin the performance of the timer.

The time delay between exposure of the passive timer to a low pressureenvironment and the subsequent extension of the actuator rod 14 dependsupon the total travel designed into the system (which can beadjustable), the metering rate and accuracy of the metering valve 16,the ambient atmospheric pressure, the choice of fluid medium to becontained within fluid storage chamber 3 and expandible chamber 10, andthe frictional forces opposing movement of the plunger 13 and actuatorrod 14. Through manipulation of the aforementioned factors governingtime delays, timing cycles ranging from a few minutes to several daysmay be effected, depending upon the metering fluid used, and based on asize of less than cubic inches. The amount of force on the actuator rod14 depends also upon the cross-sectional area of expandible chamber 10.The extension of actuator rod 14 obviously can be utilized to triggermany functions in a space environment, and the parameters mentionedhereinabove affecting the time delay and rate of extension of the rodare all controllable, which further enhances the adaptability of theinstant invention to a plurality of desired functions.

The second embodiment of the present invention is shown generally inFIG. 2 at 17 and includes a cylindrical casing 18 which defines a firstfluid storage chamber 19. The outer end of the casing is closed by awall plate 20, while the inner end is provided with a wall plate 21having an axial opening 22 therein.

A cylindrical first expandible chamber 23 of bellows configuration iscontained concentrically within a relatively larger V second expandiblechamber 24 which also has walls of bellows shape. Said first and secondexpandible chambers are sealed at respective opposite ends by plates 25and 26, said chambers 23 and 24 being air-tightly sealed from eachother. The plate 25 is attached to the wall plate 21 and has a hub 25awhich extends through the opening 22, said hub having a port 25btherein. Plate 26 has an axial extension 27 to which is attached one endof the expandible chamber 23.

An actuator rod 28 is disposed within the expandible chamber 23, andslidably extends through a bore 29 formed in the hub 25a of the plate25.

A third expandible chamber 30, of bellows configuratiomds secured to theinner surface of the wall plate within the chamber 19 and is closed atits opposite ends, thereby defining a pressure tight chamber. Thechamber 30 is expandible within the chamber 19 and contains a gas, suchas air, which is at atmospheric pressure when the bellows of the chamber30 is in a contracted position.

Positioned within the chamber 19 and connected to the plate 26 is ametering valve 31 which communicates between the interior of saidchamber 19 and the interior of the second expandible chamber 24 througha T-shaped port 32 located in the extension 27 of the plate 26. Thevalve 31 may comprise a Lee Viscojet" previously mentioned hereinabove.A fluid, which is preferably a liquid, contained in both fluid storagechamber 19 and the expandible chamber 24, is metered by the valve 31between the two chambers.

The first expandible chamber 23 is vented to ambient pressure throughthe port b. Pressure within chamber 23 therefore approaches zero onexposure to a vacuum, such as the vacuum of outer space. Gas at standardatmospheric pressure contained within third expandible chamber transmitsits one atmosphere pressure through the fluid in fluid storage chamber19 and across the frontal area of plate 26 and of first and secondexpandible chambers 23 and 24, thereby impressing a force on saidexpandible chambers 23 and 24 equal to one atmosphere multiplied by therespective frontal areas of said chambers. If the diameter of theexpandible chamber 23 is one-tenth the diameter of expandible chamber24. a pressure increase of one-tenth atmosphere is experienced inexpandible chamber 24. This differential pressure causes fluid flow fromthe chamber 24 to the fluid storage chamber 19 through the meteringvalve 31. As the pressure in expandible chamber 24 drops, said chamber24 contracts, moving the actuator rod 28 through the plate 25. The thirdexpandible chamber 30 then expands to fill the internal volume increaseof fluid storage chamber 19. The volume of the expandible chamber 30 ison the order of thirty times the volume of the first expandible chamber23 so that the pressure within said chamber 30 never drops more thanabout 3 percent. The entire system returns to neutral, or pre-launch,condition when the ambient pressure is returned to one atmosphere, thuspermitting test cycles to be accomplished readily. In-flight temperaturechanges should have only a moderate effect on performance, about a 1percent change in time for each [5C change in temperature. Thisconfiguration could be made to delay, for a year or more, depending onthe metering fluid used and based on a size of less than 10 cubicinches.

A third embodiment, shown in FIG. 3, comprises a casing 33 ofcylindrical shape which defines a fluid storage chamber 34 which issealed at respective ends by wall plates 35 and 36, plate 36 having anaxial opening 360! therein. A cylindrical first expandible chamber 37 ofbellows configuration is contained concentrically within a relativelylarger second expandible chamber 38 which also is of bellows shape. Thechambers 37 and 38 are sealed at respective ends by plates 39 and 40,said chambers 37 and 38 being air-tightly sealed from each other. Theplate 39 has an axial extension 41 to which is attached one end of thefirst expandible chamber 37. The plate 40 is attached to the end wall 36and has a port 42 therein. The plate 40 also has a hub 40a which extendsthrough the opening 360, said hub having a port 42 therein.

An actuator rod 43 is disposed within the expandible chamber 37, issecured to the extension 41 of plate 39, and slidably extends through abore 44 in the plate 40.

Positioned within the chamber 34 and connected to the plate 39 is ametering valve 45 which communicates between the interior of saidchamber 34 and the interior of the second expandible chamber 38 througha T-shaped port 46 located in the extension 41 of the plate 39. Thevalve 45 may comprise the Lee Viscojet previously described. A fluid,more preferably a gas in this particular case, contained in both thefluid storage chamber 34 and the second expandible chamber 38, ismetered by the valve 45 between said chambers.

The first expandible chamber 37 is vented to ambient pressure throughthe port 42. Pressure within the chamber 37 therefore approaches zero onexposure to a vacuum, such as would be experienced on a spacecraft inthe environment of outer space. By adjusting the frontal areas of thefirst and second expandible chambers 37 and 38 varying differentialpressures can be applied across the metering valve 45 between fluidstorage chamber 34 and the second expandible chamber 38. For example, ifthe area of second expandible chamber 38 is times that of the volume offirst expandible chamber 37, the one atmosphere of pressure in the fluidstorage chamber 34 would impress a force of one atmosphere times thefrontal area of the two expandible chambers on the plate 39 of saidexpandible chambers. A resulting increase in pressure of onehundredthatmosphere in the second expandible chamber 38 would be experienced,causing extremely slow internal metering of gas between the fluidstorage chamber 34 and the second expandible chamber 38. The onlylimitation is that the force thus generated must be enough to overcomefriction and the spring forces of the bellows. The actuator rod 43 wouldgradually move on contraction of the second expandible chamber 38 toinitiate some work function.

It is believed apparent that many variations and modifications of thepresent invention are possible in light of the above description. lt istherefore to be understood that, within the scope of the appendedclaims, the invention is not to be limited to ,the particularconstruction or uses described in these embodiments, it being consideredthat minor changes in construction may be permitted within the scope ofthe appended claims.

lclaim:

l. A passive timer comprising:

casing means defining a chamber of fixed volume;

a fluid medium contained within said chamber at a predeterminedpressure;

a first pressure-responsive means disposed within said chamber;

a second pressure-responsive means disposed within said firstpressure-responsive means;

said casing means having a port communicating the interior of saidsecond pressure-responsive means with ambient pressure;

an actuator rod carried by the second pressure-responsive means andextending slidably through the casing means; and

metering means disposed internally of the casing means for permittingflow of the fluid medium at a controlled rate between the interior ofsaid casing means and the interior of the first pressure-responsivemeans, said metering means being operable on exposure of the timer to anenvironment of lower pressure than that predetermined pressure existingin said casing means, metering of the fluid medium causing actuation ofthe second pressureresponsive means for actuating said actuator rod.

2. The passive timer of claim 1, wherein said first and secondpressure-responsive means comprises expandible bellows.

3. The passive timer of claim 1, and further comprising a thirdpressure-responsive means disposed within said casing means, said thirdpressure-responsive means being closed at its opposite ends and definingan expandible chamber.

4. The passive timer of claim 2, wherein said third pressureresponsivemeans comprises expandible bellows.

